The delivery of a drug by inhalation allows deposition of the drug in different sections of the respiratory tract, e.g., throat, trachea, bronchi and alveoli. Generally, the smaller the particle size, the longer the particle will remain suspended in air and the farther down the respiratory tract the drug can be delivered. Corticosteroids are delivered by inhalation using nebulizers, metered dose inhalers, or dry powder inhalers. The principle advantages of nebulizers over other methods of pulmonary installation are that patient cooperation is not required and the delivery of higher doses of medication is easier. The main concerns about nebulizers, however, are their increased cost, reduced portability and the inconvenience of needing to prepare medication beforehand and the increased time requirement for administering a treatment. A method of improving the administration of drugs, such as corticosteroids by nebulization would be desired.
Budesonide ((R,S)-11β,16α,17,21-tetrahydroxypregna-1,4-diene-3,20-dione cyclic 16,17-acetal with butyraldehyde; C25H34O6; Mw: 430.5) is well known. It is provided commercially as a mixture of two isomers (22R and 22S). Budesonide is an anti-inflammatory corticosteroid that exhibits potent glucocorticoid activity. Administration of budesonide is indicated for maintenance treatment of asthma and as prophylactic therapy in children.
Commercial formulations of budesonide are sold by AstraZeneca LP (Wilmington, Del.) under the trademarks ENTOCORT™ EC, PULMICORT RESPULES®, Rhinocort Aqua®, Rhinocort® Nasal Inhaler and Pulmicort Turbuhaler®, and under its generic name. PULMICORT RESPULES® suspension, which is a sterile aqueous suspension of micronized budesonide, is administered by inhalation using a nebulizer, in particular a compressed air driven jet nebulizer that delivers from 2 to 18% of the drug mass contained in the nominal charge. The general formulation for a unit dose of the PULMICORT RESPULES is set forth in U.S. Pat. No. 6,598,603, and it is an aqueous suspension in which budesonide is suspended in an aqueous medium comprising about 0.05 to 1.0 mg of budesonide, 0.05 to 0.15 mg of NaEDTA, 8.0 to 9.0 mg of NaCl, 0.15 to 0.25 mg of polysorbate, 0.25 to 0.30 mg of anhydrous citric acid, and 0.45 to 0.55 mg of sodium citrate per one ml of water. RHINOCORT® NASAL INHALER™ is a metered-dose pressurized aerosol unit containing a suspension of micronized budesonide in a mixture of propellants. RHINOCORT® AQUA™ is an unscented metered-dose manual-pump spray formulation containing a suspension of micronized budesonide in an aqueous medium. The suspensions should not be administered with an ultrasonic nebulizer.
The desired properties of a liquid for nebulization generally include: 1) reduced viscosity; 2) sterile medium; 3) reduced surface tension; 4) stability toward the mechanism of the nebulizer; 5) moderate pH of about 4-10; 6) ability to form droplets with an MMAD of <5 μm or preferably <3 μm; 7) absence of irritating preservatives and stabilizing agents; 8) suitable tonicity. On the one hand, suspensions possess some advantages but on the other hand solutions possess other advantages.
Smaldone et al. (J. Aerosol Med. (1998), 11, 113-125) disclose the results of a study on the in vitro determination of inhaled mass and particle distribution of a budesonide suspension. They conclude that 2%-18% of the nebulizer's charge of budesonide was delivered from the suspension, meaning that budesonide delivery was incomplete resulting in a significant waste of drug. In the thirteen most efficient systems, the suspension can be nebulized sufficiently well for lower respiratory tract delivery.
Another study further demonstrated the highly variable efficiency of nebulization from one nebulizer to another. Barry et al. (J. Allergy Clin. Immunol. (1998), 320-321) state that this variability should be taken into account when treating patients with nebulized budesonide. Berg et al. (J. Aerosol Sci. (1998), 19(7), 1101-1104) also report the highly variable efficiency of nebulization of PULMICORT™ suspension from one nebulizer to the next. Moreover, the mass mean aerodynamic diameter (MMAD) of the nebulized droplets is highly variable from one nebulizer to the next. In general, suspensions are less efficiently nebulized than solutions, O'Riordan (Respiratory Care, (2002), 1305-1313). Inhaled corticosteroids are utilized in the treatment of asthma and are of significant benefit because they are delivered directly to the site of action, the lung. The goal of an inhaled corticosteroid is to provide localized therapy with immediate drug activity in the lungs. Inhaled corticosteroids are well absorbed from the lungs. In fact, it can be assumed that all of the drug available at the receptor site in the lungs will be absorbed systemically. However, it is well known that using current methods and formulations the greater part of an inhaled corticosteroid dose is swallowed and becomes available for oral absorption, resulting in unwanted systemic effects. For inhaled corticosteroids, high pulmonary availability is more important than high oral bioavailability because the lung is the target organ. A product with high pulmonary availability has greater potential to exert positive effects in the lung. The ideal inhaled corticosteroid formulation would provide minimum oral delivery thereby reducing the likelihood of systemic adverse effects.
The majority of the corticosteroid dose delivered to the lung is absorbed and available systemically. For the portion of the inhaled corticosteroid dose delivered orally, bioavailability depends upon absorption from the GI tract and the extent of first pass metabolism in the liver. Since this oral component of corticosteroid drug delivery does not provide any beneficial therapeutic effect but can increase systemic side effects, it is desirable for the oral bioavailability of inhaled corticosteroid to be relatively low.
Both particle size and formulation influence the efficacy of an inhaled corticosteroid. The formulation of a drug has a significant impact on the delivery of that drug to the lungs, and therefore its efficacy. Most important in the delivery of drug to the lung are the aerosol vehicle and the size of the particles delivered. Additionally, a reduced degree of pulmonary deposition suggests a greater degree of oropharyngeal deposition. Due to a particular formulation employed, some corticosteroids are more likely to be deposited in the mouth and throat and may cause local adverse effects.
While receptor distribution is the major determinant of bronchodilator efficacy, particle size appears to be more important in determining the efficacy of an inhaled corticodsteroid. The smallest airways have an internal perimeter of 2 micrometers (mcm) or less. Thus, an inhaler with particles having a mean aerodynamic diameter of 1 mcm should have a greater respirable fraction than an inhaler with particles that have an average diameter of 3.5 to 4 mcm. For patients with obstructive lung disease, all particles should ideally be no greater than 2 to 3 mcm. A particle that is small (less than 5 mcm) is more likely to be inhaled into the smaller airways of the lungs, thus improving efficacy. In contrast, particles that are larger than 5 mcm can be deposited in the mouth and throat, both reducing the proportion of particles that reach the lungs and potentially causing local adverse effects such as oral candidiasis and hoarseness (dysphonia). Particles having a mass median aerodynamic diameter (MMAD) of close to 1 mcm are considered to have a greater respirable fraction per dose than those with a diameter of 3.5 mcm or greater.
A further disadvantage to the nebulization of budesonide suspensions is the need to generate very small droplets, MMAD of about <3 μm. Since the nebulized droplets are so small, then the micronized budesonide must be even smaller or in the range of 0.5-2.0 μm and the particles should have a narrow particle size distribution. Generation of such particles is difficult.
Even so, efforts have been made to improve the nebulization of budesonide suspensions with ultrasonic nebulizers by using submicron-sized particles (Keller et al. in Respiratory Drug Delivery VIII (2002), 197-206). A suspension of nanoparticles (0.1-1.0 μm) of the corticosteroid might be used to increase the proportion of respirable particles as compared to a coarser suspension as in the PULMICORT™ suspension. No improvement over PULMICORT™ suspension (about 4.4 μm budesonide particle size in suspension) was observed. Moreover, concerns exist regarding the use of nanosuspensions in that the small particles (<0.05 μm) may induce an allergic response in a subject. Sheffield Pharmaceuticals, Inc. (St. Louis, Mo.; “The Pharmacokinetics of Nebulized Nanocrystal Budesonide Suspension in Healthy Volunteers”, Kraft, et al. in J. Clin. Pharmacol., (2004), 44:67-72) has disclosed the preparation and evaluation of UDB (unit dose budesonide), which is a suspension-based formulation containing nanoparticles of budesonide dispersed in a liquid medium. This product is being developed by MAP Pharmaceuticals, Inc. (Mountain View, Calif.).
The inhalation of drug particles as opposed to dissolved drug is known to be disadvantageous. Brain et al. (Bronchial Asthma, 2nd Ed. (Ed. E. B. Weis et al., Little Brown & Co. (1985), pp. 594-603) report that less soluble particles that deposit on the mucous blanket covering pulmonary airways and the nasal passages are moved toward the pharynx by the cilia. Such particles would include the larger drug particles deposited in the upper respiratory tract. Mucus, cells and debris coming from the nasal cavities and the lungs meet at the pharynx, mix with saliva, and enter the gastrointestinal tract upon being swallowed. Reportedly, by this mechanism, particles are removed from the lungs with half-times of minutes to hours. Accordingly, there is little time for solubilization of slowly dissolving drugs, such as budesonide. In contrast, particles deposited in the nonciliated compartments, such as the alveoli, have much longer residence times. Since it is difficult to generate very small particles of budesonide for deep lung deposition, much of the inhaled suspension would likely be found in the upper to middle respiratory tract. However, it is much easier to generate small droplets from a solution than it is from a suspension of solids. For these reasons, nebulization of a budesonide-containing solution should be preferred over that of a suspension.
O'Riordan (Respiratory Care (2002 November), 47(11), 1305-1313) states that drugs can be delivered by nebulization of either solutions or suspensions, but that in general, nebulization of a solution is preferred over that of a suspension. He states that ultrasonic nebulizers should not be used on suspensions and should be used only on solutions.
O'Callaghan (Thorax, (1990), 45, 109-111), Storr et al. (Arch. Dis. Child (1986), 61, 270-273), and Webb et al. (Arch. Dis. Child (1986), 61, 1108-1110) suggest that nebulization of corticosteroid (in particular beclomethasone) solutions may be preferred over that of suspensions because the latter may be inefficient if the nebulized particles are too large to enter the lung in therapeutically effective amounts. However, data presented by O'Callaghan (J. Pharm. Pharmacol. (2002), 54, 565-569) on the nebulization of flunisolide solution versus suspension showed that the two performed similarly. Therefore, it cannot be generalized that nebulization of a solution is preferred over that of a suspension.
Accordingly, there is a widely recognized need for a non-suspension formulation comprising a corticosteroid for administration via nebulization. However, the PULMICORT® suspension unit dose formulation is widely available and accepted in the field of inhalation therapy. It would be of great benefit to this field of therapy to provide a method of improving the administration of the PULMICORT® suspension unit dose formulation, or more generally, of a suspension unit dose formulation containing a corticosteroid.
However, the current focus in nebulizer therapy is to administer higher concentrations of drug, use solution, preferably predominantly aqueous-based solutions in preference to non-aqueous or alcoholic or non-aqueous alcoholic solutions or suspensions if possible, minimize treatment time, synchronize nebulization with inhalation, and administer smaller droplets for deeper lung deposition of drug.
Corticosteroid-containing solutions for nebulization are known. There are a number of different ways to prepare solutions for nebulization. These generally have been prepared by the addition of a cosolvent, surfactant, or buffer. However, cosolvents, such as ethanol, polyethylene glycol and propylene glycol are only tolerated in low amounts when administered by inhalation due to irritation of the respiratory tract. There are limits to acceptable levels of these cosolvents in inhaled products. Typically, the cosolvents make up less than about 35% by weight of the nebulized composition, although it is the total dose of cosolvent as well as its concentration that determines these limits. The limits are set by the propensity of these solvents either to cause local irritation of lung tissue, to form hyperosmotic solutions that would draw fluid into the lungs, and/or to intoxicate the patient. In addition, most potential hydrophobic therapeutic agents are not sufficiently soluble in these cosolvent mixtures.
Saidi et al. (U.S. Pat. No. 6,241,969) disclose the preparation of corticosteroid-containing solutions for nasal and pulmonary delivery. The dissolved corticosteroids are present in a concentrated, essentially non-aqueous form for storage or in a diluted, aqueous-based form for administration.
Lintz et al. (AAPS Annual Meeting and Exposition, 2004) disclose the preparation of liquid formulations containing budesonide, water, citrate salt, sodium chloride and alcohol, propylene glycol and/or surfactant, such as Tween, Pluronic, or phospholipids with HLB-values between 10 and 20.
An alternative approach to administration of the PULMICORT™ suspension is administration of a liposome formulation. Waldrep et al. (J. Aerosol Med. (1994), 7(2), 135-145) reportedly succeeded in preparing a liposome formulation of budesonide and phosphatidylcholine derivatives.
None of the above-identified formulations has provided a method of improving the administration of a suspension-based unit dose formulation containing a corticosteroid. Instead, the general focus of the art has been to completely circumvent formulating a suspension by first preparing a liquid formulation that is then divided into multiple unit doses that are packaged for marketing and then sold for use.
Solubilization of drugs by cyclodextrins and their derivatives is well known. Cyclodextrins are cyclic carbohydrates derived from starch. The unmodified cyclodextrins differ by the number of glucopyranose units joined together in the cylindrical structure. The parent cyclodextrins contain 6, 7, or 8 glucopyranose units and are referred to as α-, β-, and γ-cyclodextrin respectively. Each cyclodextrin subunit has secondary hydroxyl groups at the 2 and 3 positions and a primary hydroxyl group at the 6-position. The cyclodextrins may be pictured as hollow truncated cones with hydrophilic exterior surfaces and hydrophobic interior cavities. In aqueous solutions, these hydrophobic cavities provide a haven for hydrophobic organic compounds that can fit all or part of their structure into these cavities. This process, known as inclusion complexation, may result in increased apparent aqueous solubility and stability for the complexed drug. The complex is stabilized by hydrophobic interactions and does not involve the formation of any covalent bonds.
This dynamic and reversible equilibrium process can be described by Equations 1 and 2, where the amount in the complexed form is a function of the concentrations of the drug and cyclodextrin, and the equilibrium or binding constant, Kb. When cyclodextrin formulations are administered by injection into the blood stream, the complex rapidly dissociates due to the effects of dilution and non-specific binding of the drug to blood and tissue components.
                    Drug        +                  Cyclodextrin          ⁢                      ⟷                          K              b                                ⁢          Complex                                    Equation        ⁢                                  ⁢        1                                          K          b                =                              ⌊            Complex            ⌋                                              [              Drug              ]                        ⁡                          [              Cyclodextrin              ]                                                          Equation        ⁢                                  ⁢        2            
Binding constants of cyclodextrin and an active agent can be determined by the equilibrium solubility technique (T. Higuchi et al. in “Advances in Analytical Chemistry and Instrumentation Vol. 4”; C. N. Reilly ed.; John Wiley & Sons, Inc, 1965, pp. 117-212). Generally, the higher the concentration of cyclodextrin, the more the equilibrium process of Equations 1 and 2 is shifted to the formation of more complex, meaning that the concentration of free drug is generally decreased by increasing the concentration of cyclodextrin in solution.
The underivatized parent cyclodextrins are known to interact with human tissues and extract cholesterol and other membrane components, particularly upon accumulation in the kidney tubule cells, leading to toxic and sometimes fatal renal effects.
The parent cyclodextrins often exhibit a differing affinity for any given substrate. For example, γ-cyclodextrin often forms complexes with limited solubility, resulting in solubility curves of the type Bs. This behavior is known for a large number of steroids which imposes serious limitations towards the use of γ-CD in liquid preparations. β-CD, however, does not complex well with a host of different classes of compounds. It has been shown for β-CD and γ-CD that derivatization, e.g. alkylation, results in not only better aqueous solubility of the derivatives compared to the parent CD, but also changes the type of solubility curves from the limiting Bs-type to the more linear A-type curve (Bernd W. Muller and Ulrich Brauns, “Change of Phase-Solubility Behavior by Gamma-Cyclodextrin Derivatization”, Pharmaceutical Research (1985) p 309-310).
Chemical modification of the parent cyclodextrins (usually at the hydroxyls) has resulted in derivatives with improved safety while retaining or improving the complexation ability. Of the numerous derivatized cyclodextrins prepared to date, only two appear to be commercially viable: the 2-hydroxypropyl derivatives (HP-CD; neutral cyclodextrins being commercially developed by Janssen and others), and the sulfoalkyl ether derivatives, such as sulfobutyl ether, (SBE-CD; anionic cyclodextrins being developed by CyDex, Inc.) However, the HP-β-CD still
possesses toxicity that the SBE-CD does not.
U.S. Pat. No. 5,376,645 and U.S. Pat. No. 5,134,127 to Stella et al., U.S. Pat. No. 3,426,011 to Parmerter et al., Lammers et al. (Recl. Trav. Chim. Pays-Bas (1972), 91(6), 733-742); Staerke (1971), 23(5), 167-171) and Qu et al. (J. Inclusion Phenom. Macro. Chem., (2002), 43, 213-221) disclose sulfoalkyl ether derivatized cyclodextrins. The references suggest that SAE-CD should be suitable for solubilizing a range of different compounds. However, Stella discloses that the molar ratio of sulfoalkyl ether derivatized cyclodextrin to active ingredient suitable for solubilization of the active ingredient, even a corticosteroid, in water ranges from 10:1 to 1:10.
A sulfobutyl ether derivative of beta cyclodextrin (SBE-β-CD), in particular the derivative with an average of about 7 substituents per cyclodextrin molecule (SBE7-β-CD), has been commercialized by CyDex, Inc. as CAPTISOL®. The anionic sulfobutyl ether substituent dramatically improves the aqueous solubility of the parent cyclodextrin. In addition, the presence of the charges decreases the ability of the molecule to complex with cholesterol as compared to the hydroxypropyl derivative. Reversible, non-covalent, complexation of drugs with CAPTISOL® cyclodextrin generally allows for increased solubility and stability of drugs in aqueous solutions. While CAPTISOL® is a relatively new but known cyclodextrin, its use in the preparation of corticosteroid-containing solutions for nebulization has not previously been evaluated.
Hemolytic assays are generally used in the field of parenteral formulations to predict whether or not a particular formulation is likely to be unsuitable for injection into the bloodstream of a subject. If the formulation being tested induces a significant amount of hemolysis, that formulation will generally be considered unsuitable for administration to a subject. It is generally expected that a higher osmolality is associated with a higher hemolytic potential. As depicted in FIG. 1 (Thompson, D. O., Critical Reviews in Therapeutic Drug Carrier Systems, (1997), 14(1), 1-104), the hemolytic behavior of the CAPTISOL® is compared to the same for the parent β-Cyclodextrin, the commercially available hydroxypropyl derivatives, ENCAPSIN™ cyclodextrin (degree of substitution-3-4) and MOLECUSOL®, cyclodextrin (degree of substitution-7-8), and two other sulfobutyl ether derivatives, SBE1-β-CD and SBE4-β-CD. Unlike the other cyclodextrin derivatives, sulfoalkyl ether (SAE-CD) derivatives, in particular those such as the CAPTISOL® (degree of substitution˜7) and SBE4-β-CD (degree of substitution˜4), show essentially no hemolytic behavior and exhibit substantially lower membrane damaging potential than the commercially available hydroxypropyl derivatives at concentrations typically used to solubilize pharmaceutical formulations. The range of concentrations depicted in the figure includes the concentrations typically used to solubilize pharmaceutical formulations when initially diluted in the blood stream after injection. After oral administration, SAE-CD does not undergo significant systemic absorption.
The osmolality of a formulation is generally associated with its hemolytic potential: the higher the osmolality (or the more hypertonic), the greater the hemolytic potential. Zannou et al. (“Osmotic properties of sulfobutyl ether and hydroxypropyl cyclodextrins”, Pharma. Res. (2001), 18(8), 1226-1231) compared the osmolality of solutions containing SBE-CD and HP-CD. As depicted in FIG. 2, the SBE-CD containing solutions have a greater osmolality than HP-CD containing solutions comprising similar concentrations of cyclodextrin derivative. Thus, it is surprising that SAE-CD exhibits lower hemolysis than does HP-CD at equivalent concentrations, even though HP-CD has a lower osmolality.
Methylated cyclodextrins have been prepared and their hemolytic effect on human erythrocytes has been evaluated. These cyclodextrins were found to cause moderate to severe hemolysis (Jodal et al., Proc. 4th Int. Symp. Cyclodextrins, (1988), 421-425; Yoshida et al., Int. J. Pharm., (1988), 46(3), 217-222).
Administration of cyclodextrins into the lungs of a mammal may not be acceptable. In fact, literature exists on the potential or observed toxicity of native cyclodextrins and cyclodextrin derivatives. The NTP Chemical Repository indicates that α-cyclodextrin may be harmful by inhalation, Nimbalkar et al. (Biotechnol. Appl. Biochem. (2001), 33, 123-125) cautions on the pulmonary use of an HP-β-CD/diacetyldapsone complex due to its initial effect of delaying cell growth of lung cells.
Even so, a number of studies regarding the use of cyclodextrins for inhalation have been reported although none have been commercialized. The studies suggest that different drug-cyclodextrin combinations will be required for specific optimal or even useful inhaled or intra-nasal formulations. Attempts have been made to develop cyclodextrin-containing powders and solutions for buccal, pulmonary and/or nasal delivery.
U.S. Pat. No. 5,914,122 to Otterbeck et al. discloses the preparation of stable budesonide-containing solutions for nebulization. They demonstrate the use of cyclodextrin, such as β-CD, γ-CD or HP-β-CD, and/or EDTA as a stabilizer. Cyclodextrin is also suggested as a solubilizer for increasing the concentration of budesonide in solution. In each case, the greatest shelf-life they report for any of their formulations is, in terms of acceptable retention of the active ingredient, only three to six months.
U.S. Pregrant Patent Publication No. 20020055496 to McCoy et al. discloses essentially non-aqueous intra-oral formulations containing HP-β-CD. The formulations may be administered with an aerosol, spray pump or propellant.
Russian Patent No. 2180217 to Chuchalin discloses a stable budesonide-containing solution for inhalation. The solution comprises budesonide, propylene glycol, poly(ethylene oxide), succinic acid, Triton B, nipazole, thiourea, water, and optionally HP-β-CD.
Müller et al. (Proceed. Int'l. Symp. Control. Rel. Bioact. Mater. (1997), 24, 69-70) discloses the results of a study on the preparation of budesonide microparticles by an ASES (Aerosol Solvent Extraction System) supercritical carbon dioxide process for use in a dry powder inhaler. HP-β-CD is suggested as a carrier for a powder.
Müller et al. (U.S. Pat. No. 6,407,079) discloses pharmaceutical compositions containing HP-β-CD. They suggest that nasal administration of a solution containing the cyclodextrin is possible.
The art recognizes that it may be necessary to evaluate structurally related variations of a particular type of cyclodextrin derivative in order to optimize the binding of a particular compound with that type of cyclodextrin derivative. However, it is often the case that there are not extreme differences in the binding of a particular compound with a first embodiment versus a second embodiment of a particular cyclodextrin derivative. For example, cases where there are extreme differences in the binding of a particular therapeutic agent for a first cyclodextrin derivative versus a structurally related second cyclodextrin derivative are uncommon. When such situations do exist, they are unexpected. Worth et al. (24th International Symposium on Controlled Release of Bioactive Materials (1997)) disclose the results of a study evaluating the utility of steroid/cyclodextrin complexes for pulmonary delivery. In side-by-side comparisons, β-CD, SBE7-β-CD, and HP-β-CD were evaluated according to their ability to form inclusion complexes with beclomethasone dipropionate (BDP) and its active metabolite beclomethasone monopropionate (BMP). BMP was more easily solubilized with a cyclodextrin, and the observed order of solubilizing power was: HP-β-CD (highest)>β-CD>SBE7-β-CD. Thus, the artisan would expect that SAE-CD derivatives would not be as suitable for use in solubilizing corticosteroids such as BMP or BDP. Although no results regarding actual utility in an inhaled formulation were disclosed, they suggest that BMP rather than BDP would be a better alternative for development of a nebulizer solution.
Kinnarinen et al. (11th International Cyclodextrin Symposium CD, (2002)) disclose the results of a study of the in vitro pulmonary deposition of a budesonide/γ-CD inclusion complex for dry powder inhalation. No advantage was observed by complexation with γ-CD. Vozone et al. (11th International Cyclodextrin Symposium CD, (2002)) disclose the results of a study on the complexation of budesonide with γ-cyclodextrin for use in dry powder inhalation. No difference was observed within emitted doses of the cyclodextrin complex or a physical mixture of budesonide and the CD. But, a difference observed in the fine particle fraction of both formulations suggested that use of a cyclodextrin complex for pulmonary drug delivery might increase the respirable fraction of the dry powder.
Pinto et al. (S.T.P. Pharma. Sciences (1999), 9(3), 253-256) disclose the results of a study on the use of HP-β-CD in an inhalable dry powder formulation for beclomethasone. The HP-β-CD was evaluated as a complex or physical mixture with the drug in a study of in vitro deposition of the emitted dose from a MICRO-HALER™ inhalation device. The amount of respirable drug fraction was reportedly highest with the complex and lowest with the micronized drug alone.
Rajewski et al. (J. Pharm. Sci. (1996), 85(11), 1142-1169) provide a review of the pharmaceutical applications of cyclodextrins. In that review, they cite studies evaluating the use of cyclodextrin complexes in dry powder inhalation systems.
Shao et al (Eur. J. Pharm. Biopharm. (1994), 40, 283-288) reported on the effectiveness of cyclodextrins as pulmonary absorption promoters. The relative effectiveness of cyclodextrins in enhancing pulmonary insulin absorption, as measured by pharmacodynamics, and relative efficiency was ranked as follows: dimethyl-β-cyclodextrin>α-cyclodextrin>β-cyclodextrin>γ-cyclodextrin>hydroxypropyl-β-cyclodextrin. In view of this report, the artisan would expect the water soluble derivative of γ-CD to be less suitable for delivering compounds via inhalation than the respective derivative of γ-CD because the underivatized β-CD is more suitable than the underivatized γ-CD.
Williams et al. (Eur. J. Pharm. Biopharm. (1999 March), 47(2), 145-52) reported the results of a study to determine the influence of the formulation technique for 2-hydroxypropyl-beta-cyclodextrin (HP-β-CD) on the stability of aspirin in a suspension-based pressurized metered-dose inhaler (pMDI) formulation containing a hydrofluoroalkane (HFA) propellant. HP-γ-CD was formulated in a pMDI as a lyophilized inclusion complex or a physical mixture with aspirin. Aspirin in the lyophilized inclusion complex exhibited the most significant degree of degradation during the 6-months storage, while aspirin alone in the pMDI demonstrated a moderate degree of degradation. Aspirin formulated in the physical mixture displayed the least degree of degradation. Reportedly, HP-β-CD may be used to enhance the stability of a chemically labile drug, but the drug stability may be affected by the method of preparation of the formulation.
Gudmundsdottir et al. (Pharmazie (2001 December), 56(12), 963-6) disclose the results of a study in which midazolam was formulated in aqueous sulfobutylether-beta-cyclodextrin buffer solution. The nasal spray was tested in healthy volunteers and compared to intravenous midazolam in an open crossover trial. The nasal formulation reportedly approaches the intravenous form in speed of absorption, serum concentration and clinical sedation effect. No serious side effects were observed.
Srichana et al. (Respir. Med. (2001 June), 95(6), 513-9) report the results of a study to develop a new carrier in dry powder aerosols. Two types of cyclodextrin were chosen; gamma cyclodextrin (γ-CD) and dimethyl-beta-cyclodextrin (DMCD) as carriers in dry powder formulations. Salbutamol was used as a model drug and a control formulation containing lactose and the drug was included. A twin-stage impinger (TSI) was used to evaluate in delivery efficiency of those dry powder formulations. From the results obtained, it was found that the formulation containing γ-CD-enhanced drug delivery to the lower stage of the TSI (deposition=65%) much greater than that of both formulations containing DMCD (50%) and the control formulation (40%) (P<0.05). The haemolysis of red blood cells incubated with the DMCD complex was higher than that obtained in the γ-CD complex. The drug release in both formulations containing γ-CD and DMCD was fast (over 70% was released in 5 min) and nearly all the drug was released within 30 min.
van der Kuy et al. (Eur. Clin. Pharmacol. (1999 November), 55(9), 677-80) report the results of the pharmacokinetic properties of two intranasal preparations of dihydroergotamine mesylate (DHEM)-containing formulation using a commercially available intranasal preparation. The formulations also contained randomly methylated β-cyclodextrin (RAMEB). No statistically significant differences were found in maximum plasma concentration (Cmax), time to reach Cmax (tmax), area under plasma concentration-time curve (AUC0-8 h), Frel(t=8 h) and Cmax/AUC(t=8 h) for the three intranasal preparations. The results indicate that the pharmacokinetic properties of the intranasal preparations are not significantly different from the commercially available nasal spray.
U.S. Pat. Nos. 5,942,251 and 5,756,483 to Merkus cover pharmaceutical compositions for the intranasal administration of dihydroergotamine, apomorphine and morphine comprising one of these pharmacologically active ingredients in combination with a cyclodextrin and/or a disaccharide and/or a polysaccharide and/or a sugar alcohol.
U.S. Pat. No. 5,955,454 discloses a pharmaceutical preparation suitable for nasal administration containing a progestogen and a methylated β-cyclodextrin having a degree of substitution of between 0.5 and 3.0.
U.S. Pat. No. 5,977,070 to Piazza et al. discloses a pharmaceutical composition for the nasal delivery of compounds useful for treating osteoporosis, comprising an effective amount of a physiologically active truncated analog of PTH or PTHrp, or salt thereof and an absorption enhancer selected from the group consisting of dimethyl-β-cyclodextrin.
U.S. Pat. No. 6,436,902 to Backstrom et al. discloses compositions and methods for the pulmonary administration of a parathyroid hormone in the form of a dry powder suitable for inhalation in which at least 50% of the dry powder consists of (a) particles having a diameter of up to 10 microns; or (b) agglomerates of such particles. A dry powder inhaler device contains a preparation consisting of a dry powder comprising (i) a parathyroid hormone (PTH), and (ii) a substance that enhances the absorption of PTH in the lower respiratory tract, wherein at least 50% of (i) and (ii) consists of primary particles having a diameter of up to 10 microns, and wherein the substance is selected from the group consisting of a salt of a fatty acid, a bile salt or derivative thereof, a phospholipid, and a cyclodextrin or derivative thereof.
U.S. Pat. No. 6,518,239 to Kuo et al. discloses a dispersible aerosol formulation comprising an active agent and a dipeptide or tripeptide for aerosolized administration to the lung. The compositions reportedly may also include polymeric excipients/additives, e.g., polyvinylpyrrolidones, derivatized celluloses such as hydroxymethylcellulose, hydroxyethylcellulose, and hydroxypropyl methylcellulose, Ficolls (a polymeric sugar), hydroxyethylstarch, dextrates (e.g., cyclodextrins, such as 2-hydroxypropyl-β-cyclodextrin and sulfobutylether-β-cyclodextrin), polyethylene glycols, and pectin.
Nakate et al. (Eur. J. Pharm. Biopharm. (2003 March), 55(2), 147-54) disclose the results of a study to determine the improvement of pulmonary absorption of the cyclopeptide FK224 (low aqueous solubility) in rats by co-formulating it with beta-cyclodextrin. The purpose of the study was to investigate the effect of pulmonary delivery on the systemic absorption of FK224 in comparison with other administration routes, and to determine the bioavailability (BA) of FK224 following pulmonary administration in rats using various dosage forms. After administration of an aqueous suspension, the bioavailability was reduced to 2.7% compared with 16.8% for the solution. However, β-cyclodextrin (β-CD) was found to be an effective additive as far as improving the solubility of FK224 was concerned. The bioavailability of the aqueous suspension containing β-CD was increased to 19.2%. It was observed that both the C(max) and AUC of FK224 were increased as the amount of β-CD increased. The plasma profiles showed sustained absorption. They suggest that β-CD is an extremely effective additive as far as improving the pulmonary absorption of FK224 is concerned. They also suggest that β-CD or derivatives with various degrees of aqueous solubility are potential drug carriers for controlling pulmonary absorption.
Kobayashi et al. (Pharm. Res. (1996 January), 13(1), 80-3) disclose the results of a study on pulmonary delivery of salmon calcitonin (sCT) dry powders containing absorption enhancers in rats. After intratracheal administration of sCT dry powder and liquid (solution) preparations to rats, plasma sCT levels and calcium levels were measured. Reportedly, sCT in the dry powder and in the liquid were absorbed nearly to the same degree. Absorption enhancers (oleic acid, lecithin, citric acid, taurocholic acid, dimethyl-β-cyclodextrin, octyl-β-D-glucoside) were much more effective in the dry powder than in the solution.
Adjei et al. (Pharm. Res. (1992 February), 9(2), 244-9) disclose the results of a study on the bioavailability of leuprolide acetate following nasal and inhalation delivery to rats and healthy humans. Systemic delivery of leuprolide acetate, a luteinizing hormone releasing hormone (LHRH) agonist, was compared after inhalation (i.h.) and intranasal (i.n.) administration. The i.n. bioavailability in rats was significantly increased by α-cyclodextrin (CD), EDTA, and solution volume. Absorption ranged from 8 to 46% compared to i.v. controls. Studies in healthy human males were conducted with leuprolide acetate i.n. by spray, or inhalation aerosol (i.h.), and subcutaneous (s.c.) and intravenous (i.v.) injection. The s.c. injection was 94% bioavailable compared with i.v. The i.n. bioavailability averaged 2.4%, with significant subject-to-subject variability. Inhalation delivery gave a slightly lower intersubject variability. Mean Cmax with a 1-mg dose of solution aerosol was 0.97 ng/ml, compared with 4.4 and 11.4 ng/ml for suspension aerosols given at 1- and 2-mg bolus dosages, respectively. The mean bioavailability of the suspension aerosols (28% relative to s.c. administration) was four fold greater than that of the solution aerosol (6.6%).
CyDex (Cyclopedia (2002), 5(1), 3) discloses that SBE-CD is non-toxic to rats in an inhaled aerosol composition when present alone. They do not disclose a nebulizable composition comprising a drug, in particular a corticosteroid, and SBE-CD.
In deciding whether to administer a suspension versus solution, one must also consider the type of nebulizer to be used. The two most common types of nebulizers are the ultrasonic nebulizer and the air driven jet nebulizer. There are significant differences between the two. For example, jet nebulizers cool rather than heat the liquid in the reservoir, whereas ultrasonic nebulizers heat the liquid. While heating of the solution in reservoir can reduce the viscosity of the solution and enhance formation of droplets, excessive heating could lead to drug degradation. The ultrasonic nebulizer is quieter and provides faster delivery than the jet nebulizer, but ultrasonic nebulizers are more expensive and are not advised for the administration of the currently available steroid for nebulization. Most importantly, however, ultrasonic nebulizers generally provide a significantly higher rate of administration than do jet nebulizers.
Patients with asthma are often treated with inhaled short acting or long acting β2-agonists, inhaled anticholinergics, and inhaled corticosteroids alone, sequentially or in combination. Combinations of inhaled corticosteroids and long acting β2-agonists are known, for example budesonide plus formoterol or fluticasone plus salmeterol are available in a dry powder inhaler. However, there is no example of such combinations that are available as a solution for nebulization. Combining the medications into one solution would reduce the time required to administer the medications separately.
For inhaled corticosteroids, high pulmonary availability is more important than high oral bioavailability because the lung is the target organ. A product with high pulmonary availability has greater potential to exert positive effects in the lung. The ideal ICS would have minimum oral bioavailability, reducing the likelihood of systemic adverse effects.
Although extremely effective in the treatment of asthma, inhaled corticosteroids can have a number of adverse side effects such as oral candidiasis, hoarseness (dysphonia), and pharyngitis. Therefore, inhaled corticosteroids are best delivered by a method that minimizes the oral and/or pharyngeal deposition of the corticosteroid and instead maximizes pulmonary delivery.
Some corticosteroids posses a hydroxyl group at position 21 of the corticosteroid. Those compounds include budesonide, flunisolide, triamcinolone acetonide, beclomethasone monopropionate, and the active form of ciclesonide (desisobutyryl-ciclesonide). It is known that ciclesonide is inhaled as an inactive compound and converted by esterases in the lung to its active form, desisobutyryl-ciclesonide (des-CIC). Budesonide conjugates to form intracellular fatty acid esters, which are highly lipophilic. Budesonide forms conjugates with 5 fatty acids: oleate, palmitate, linoleate, palmitoleate, and arachidonate.
In summary, the art suggests that, in some cases, nebulization of solutions may be preferred over that of suspensions and that, in some cases, an ultrasonic nebulizer, vibrating mesh, electronic or other mechanism of aerosolization may be preferred over an air driven jet nebulizer depending upon the nebulization liquid formulations being compared. Even though the art discloses inhalable solution formulations containing a corticosteroid and cyclodextrin, the results of the art are unpredictable. In other words, the combination of one cyclodextrin with one drug does not suggest that another cyclodextrin may be suitable. Neither does the art suggest that one cyclodextrin-corticosteroid inhalable formulation will possess advantages over another cyclodextrin-corticosteroid inhalable formulation.
A need remains in the art for a stabilized aqueous solution budesonide-containing inhalable formulation that does not require the addition of preservatives and that provides significant advantages over other stabilized aqueous solution budesonide-containing inhalable formulations. A need also remains for a method of improving the administration of budesonide-containing suspension formulations by nebulization by converting the suspension to a solution.
There is also a need to develop improved systems that can solubilize water-insoluble drugs for nebulization, and to minimize the levels of cosolvent necessary to accomplish this. The ideal system would consist of non-toxic ingredients and be stable for long periods of storage at room temperature. When nebulized, it would produce respirable droplets in the less than 10 micron or less than 5 micron or less than 3 micron and a substantial portion of extra-fine aerosol in the less than about 1 micron size range.
The need continues to remain for a method of improving the administration, by nebulization, of a suspension-based unit dose formulation. Such a method would reduce the overall time of administration, increase the overall amount of drug administered, reduce the amount of drug left in the reservoir of the nebulizer, increase the portion of pulmonary deposition relative to oropharyngeal deposition of corticosteroid, and/or enhance deep lung penetration of the corticosteroid as compared to such administration, absent the improvement, of the suspension-based unit dose formulation.